Field
The present disclosure relates to a tread for a tire intended for winter driving.
Description of Related Art
A tire for winter driving, known as a snow tire, needs to have sufficient grip both on a snowy road surface and on an icy road surface. However, on these different types of ground, the way in which the tread works to achieve good grip differ and can even counter one another. On a snowy road surface attempts will be made to “claw at” the snow by creating raised pressures in specific zones of the tread. On an icy road surface the aim is to obtain the highest and most uniform possible contact pressure with the road surface.
Document U.S. Pat. No. 5,840,137 discloses a tread comprising a plurality of grooves delimited by walls. These walls are formed by a cover layer containing a material that differs from the rubber material of which the tread is made. More specifically, the material of the layer here has a mean glass transition temperature (Tg) which is lower than that of the rubber material, thus making it more rigid. Thanks to this rigidity, it can more easily claw at the snow on the snowy road surface and therefore very greatly improve the grip on this snowy road surface. However, the inventors have observed that the tread of document U.S. Pat. No. 5,840,137 does not make it possible to improve to the same extent the level of grip on an icy road surface. This tread therefore exhibits a not insignificant imbalance between, on the one hand, its performance on a snowy road surface and, on the other hand, its performance on an icy road surface.
There is therefore a need to create a tire tread that affords a better compromise between grip on a snowy road surface and grip on an icy road surface, while at the same time maintaining a very high level of grip on this snowy road surface.